Blade sharpener



FIG. 1 is a perspective view of a blade sharpener showing my new design;

FIG. 2 is a left side view thereof; and,

FIG. 3 is a right side view thereof.

The broken line showing of the raised element on the handle is for illlustrative purposes only and forms no part of the claimed design. 

The ornamental design for a blade sharpener, as shown and described. 